1. Field of the Invention
The present invention relates to a light scanning photoelectric switch.
2. Description of the Related Art
Conventionally, there has been proposed a scanning device that detects, using light such as laser, whether or not an object is present within a predetermined area that has been previously set (see Japanese Unexamined Patent Publication No. 4-310890 (Abstract), Japanese Unexamined Patent Publication No. 3-175390 (FIG. 1), and U.S. Pat. No. 5,455,669 (FIG. 4)).
A light scanning photoelectric switch is a so-called safety scanner or safety laser scanner, and scans over a detection area with light such as laser, receives the scanning light that has been reflected within the detection area, measures a distance to an object based on a difference between a light projecting timing and a light receiving timing, that is, a time difference and a known speed of light, specifies a position of the object based on a distance in each predetermined direction, outputs a safety signal indicating that a function of the device is either enabled or disabled, and disables the function of the device as needed.
As an alternative way of sensing an object without using the light scanning photoelectric switch, utilizing a mat switch or providing a light curtain in a horizontal direction can be conceivable.
A mat switch, for example, detects an approach of a worker and the like by the worker stepping on the mat switch. When using such a mat switch, a position at which the mat switch is placed is a detection area, and this can be recognized at a glance. Accordingly, it is possible to intuitively determine whether or not the mat switch is placed at a correct position. Further, similarly for a light curtain, it is also possible to intuitively determine a position for placing the light curtain based on positions at which light is projected and received.
However, such a mat switch or a light curtain has a fixed detection area which depends on a shape of an individual product, and it is necessary to prepare a number of products of different shapes, which is inconvenient for a user.
Therefore, employment of a light scanning photoelectric switch, with which setting of an area for detecting a position of an object (protection area) can be arbitrarily changed, instead of a mat switch or the like, has been proposed. However, the setting itself is complicated because an additional setting device such as a personal computer (PC) is required in order to set the protection area, installation of the light scanning photoelectric switch is difficult compared to mat switches or light curtains that practically do not require setting of the detection area.
On the other hand, in order to allow a minimum necessary setting without connecting to the PC, it is necessary to provide a display screen of a certain degree of size which displays setting contents of the protection area and a status of safety functions and failures. Further, an operating unit capable of switching the setting and display contents is also necessary. Such a display screen and an operating unit can increase a size of the photoelectric switch.